X-ray diffraction data of oriented film of PCMO grown on Nb:STO substrate.
(Color online) (a) Cross-sectional SEM image of the PCMO/Nb:STO device with Ag top electrode. The inset shows the schematic of the device structure and probe placement during measurements Arrow indicates the current direction. (b) Ag top electrode of lateral dimension 200 μm deposited on PCMO/Nb:STO film by evaporation through metal musk.
The in-plane I–V data (using four-probe arrangements) taken on the PCMO/STO film in the voltage range up to ±4 V.
(Color online) I–V curve (up to V < 1.5 V) for the virgin PCMO/Nb:STO devices (PCMO positive) before start of the voltage cycling. The solid line through the data is the fit to the model of a p-n junction with a series resistance.
(Color online) Effect of voltage cycling with the maximum voltage excursion (V max = 2, 2.5,and 3 V). The voltage bias was scanned as 0 → + V max → 0 → − V max → 0 V. (a) Voltage cycling with V max = 2V, virgin diode-like state switches to a lower resistance state (LRS1) at a forward bias of V = 1.9V and stays at LRS1 on voltage cycling (V max ≤ 2V) including the swing to reverse bias. (b) Gradual enhancement of voltage (V max) leads to transition to successive lower resistance states. On reducing the bias the lower resistance states (LRS1, LRS2, LRS3 etc.) changes back to the LRS1 state at V ≈ V*and for V < V* including the sweep in the reverse bias region, the I–V curve follows that of the LRS1 state.
(Color online) I–V curve of the final low resistance state (LRSf) obtained with V max = 3 V along with that of the I–V curve of the LRS1 state of the device. Solid line indicates the fitting curve to the model (see inset) of a p-n junction diode with a series resistance (r) and a shunt resistor (R).
Cross-sectional TEM image of the PCMO/Nb:STO device: Appearance of clear filamentary bridges connecting two electrodes can be seen.
Parameters obtained by fitting I–V data taken for different values of V max to the proposed model.
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